It's a widely held hypothesis that ecological and climatological changes had a crucial driving role in evolution throughout history. Now Penn State University geoscience professor Katherine Freeman and her graduate student, Clayton Magill, have put forth an intriguing study, which suggests that chaos in the ecosystem of East Africa drove mankind's ancestors to radically evolve 2 million years ago.

I. Life on the Chaotic Savanna

Mr. Magill comments, "The landscape early humans were inhabiting transitioned rapidly back and forth between a closed woodland and an open grassland about five to six times during a period of 200,000 years. These changes happened very abruptly, with each transition occurring over hundreds to just a few thousand years."

To examine the ecological transition that coincided with this crucial phase of hominid evolution the researchers traveled to the Olduvai Gorge in northern Tanzania, collecting lake sediments. Filtering the sediments of different ages, they performed biochemical analysis looking for fossilized chemical traces of grasses and trees.

Specifically, they sifted through sediments looking for leaf waxes, hardy biochemicals that tend to resist breakdown and survive, even over millions of years. By performing gas chromatography and mass spectrometry analyses on the various waxes, the researchers were able to pinpoint both the foliage and composition to within a couple centuries.

Biochemical analysis of local sediments in a Tanzania gorge have offered key clues as to the evolutionary path of mankind's hominid ancestors. [Image Source: Gail Ashley]

What they discovered was that the "Great Drying", which is widely proven to have occurred in Africa around 3 million years ago, was not as much of a one-way process as was previously thought. Rather, the sediments showed that the local ecosystem appears to have gone through a chaotic transition period in which the climate would fluctuate between wet and dry, before eventually gravitating fully to drier savanna.

To better understand the source of such strange and chaotic cycling, the researchers used statistical and mathematical models to formulate a hypothesis on the causes.

Explains Professor Freeman, "The orbit of the Earth around the sun slowly changes with time. These changes were tied to the local climate at Olduvai Gorge through changes in the monsoon system in Africa. Slight changes in the amount of sunshine changed the intensity of atmospheric circulation and the supply of water. The rain patterns that drive the plant patterns follow this monsoon circulation."

"We found a correlation between changes in the environment and planetary movement. We find complementary forcing mechanisms: one is the way Earth orbits, and the other is variation in ocean temperatures surrounding Africa."

II. Adversity Breeds Evolved Intelligence

The chaos would obviously cause great stress on hominids living in the region forcing them to adapt to different food sources, different landscape, and different predators. Mr. Magill and Professor Freeman suggest this was a key driver of the evolution of human intelligence.

Comments Mr. Magill, "Early humans went from having trees available to having only grasses available in just 10 to 100 generations, and their diets would have had to change in response. Changes in food availability, food type, or the way you get food can trigger evolutionary mechanisms to deal with those changes."

"The result can be increased brain size and cognition, changes in locomotion and even social changes -- how you interact with others in a group. Our data are consistent with these hypotheses. We show that the environment changed dramatically over a short time, and this variability coincides with an important period in our human evolution when the genus Homo was first established and when there was first evidence of tool use."

The research was published as a pairof papers [abstracts] in the prestigious peer-reviewed journal The Proceedings of the National Academy of Sciences (PNAS). Among the other researchers working on the team was Rutgers University earth and planetary sciences professor Gail Ashley. The research was funded by a National Science Foundation (NSF) grant.

Something is missing for me or maybe it’s just Darwinism. Maybe someone can explain it because I have a hard time believing we evolved from apes despite our similarities. If we did then early humans had to have the ability to mate with apes to produce more humans which Im not sure was possible once DNA makes a radical shift. If we didn’t mate with apes then the jump that evolution requires also requires it happened twice and at the same time to make both a man and woman because were not asexual and self-reproducing. And this would have had to occur for nearly every species on the planet a jump in DNA and the production of both a male and female so the species can reproduce. Shouldn’t we be able to find these missing links not just for ourselves but for any other species? And how does it happen that both a male and female are produced so the species lives on and reproduces?

What missing links? There are fossils found and dated that document every step of the way from a chip-like ape to modern human. There is no missing link. IT really biols down to this. the smarter ones were better at surviving, therefore thier genes reproduced more. Over time, the species as a whole gets smarter.

It's even seen in modern humans skin color. As we left Africa and went into Europe, our skin got lighter. Why? Because of Vitamin D. We need some of it, but not too much of it. The suns UV rays tens to kill it and dark skin provides protection. As we moved into colder climates, the melanin in the skin lightened to regulate the amount of vitamin D. Geneticists say that if everyone in Africa moved away to a cold and dreary climate like northern Europe, their descendants would all be white within 20-20 thousand years. We see it in cats and docs with selective breeding, and we see it in bacteria evolving immunities to antibiotics. Flood them with antibiotics and most die. The few that were stronger survive and the offspring is even stronger. They stonger breed with the stronger and multiply that by 100's of generations and you have resistant strains of bacteria.

Evolution is more than what you cite with bacterial strains becoming resistant to antibiotics. There are some major leaps that CAN'T be explained by natural selection.

Modern humans have larger brains. That along with standing upright and the changes in the hips/pelvis those required made child birth VERY dangerous. The idea of natural selection would say that these changes would have been weeded out. They aren't off-set by a greater intelligence since there is no evidence of that until long after the physiological changes.

That and natural selection doesn't generate new traits. The bacteria already had some resistance to antibiotics, which is why you can't just take one dose and be done with it. And again with the skin color: Human skin was capable of producing melanin already, changing the amount of melanin produced is not anything spectacular or evolutionary.

The transitional fossils are pretty pathetic. I'm willing to suspend disbelief a little bit and say that it is possible that the changes between Ardipithecus and Australopithecus could have happened in one generation (one gene - or set of genes - changed) but not to the point where I'd claim it as proof of anything... There should be quite a few steps between the two, which seems unlikely since they were essentially contemporary.

"Evolution is more than what you cite with bacterial strains becoming resistant to antibiotics. There are some major leaps that CAN'T be explained by natural selection.

Of course it is more than that. That is one small example we have seen over the century or so since Penecillin was developed.

"Modern humans have larger brains. That along with standing upright and the changes in the hips/pelvis those required made child birth VERY dangerous. The idea of natural selection would say that these changes would have been weeded out."

That's not how it works. Try more like this. As trees in Africa became more and more scarce there were less and less places for us to hide and the distance between 2 safe places farther and farther. This pushed our tree dwelling ancestors to have to walk to get to the next bunch of trees. Over 100's of thousands of years, those that were faster and able to stand up higher on 2 feet managed to live better, and their offspring did the same and so on and eventually we were erect. This freed up our hands to hold tools that helped us to become hunters that helped us get the protien to facilitate larger brains. Its over 100's of thousands of years.

"That and natural selection doesn't generate new traits."See previous section or google it FFS!. The info is out there. I didnt make it up.

"The transitional fossils are pretty pathetic."We have thousands of fossils that document every step of the way with backing data from our own DNA, and archaeological and geological evidence that all paint the same picture. This is why every scientist on Earth knows we evolved and anyone that thinks otherwise is either uninformed or in denial... period. As I said, the debate is long over.

Actually, the UV rays make Vit D (not destroy it). UV rays damage the skin and cause skin cancer which is why there is more melanin to protect the dermis. The increased melanin arises to protect from UV damage and skin cancer. Did you just make your comments up to fit your hypothesis?

I think you are confusing evolution with mutation. Evolution would not produce a significant change to DNA in 1 generation to where it couldn't mate with the previous generation. Therefor you wouldn't need a female and male to go through the evolution at the same time. It's a gradual change. So you wouldn't need early humans to mate with apes it was still apes mating with apes then it was slightly changed apes mating with apes and slightly changed apes. It is a fact that modern humans did mate with pre-modern man so assuming slightly evolved apes could mate with standard apes it pretty reasonable. All big cats can currently interbreed.Both a female and male didn't evolve in 1 generations into humans.

We evolved to live between both trees and grass plains. Apes and chimps only live in one of those environments, we Humans evolved to take advantage of both. Conquering multiple ecosystems favoured selected breeding of intelligence, and language to better coordinate in a social group, which led to tool making, and that gave us everything needed to migrate elsewhere. Out in the open, we required speed above all else to evade predators (or hunt them!). We're bipedal and nimble, we lost body hair and mass to remain streamlined, swift and agile. We lost muscle mass also because climbing trees and was no longer necessary and body mass since we switched to concentrated foods (meat!). We used our tools to master fire, and by extension learned to cook meat and vegtables (less energy in digesting/chewing and more nutrients since cooking is basically an externalised digestion shortcut). We became hunters instead of the hunted.

Eventually, some clever Homo Sapien would put it all together and invented the Scientific Method. Thereafter, we ruled the planet uncontested until we were wiped out by a stray asteroid (except for the Mars Colony :P).